Hidden charms

A friend of mine insists that you can get an electric shock even after an appliance has been unplugged. I've told them that they are wrong, but now I need to be sure. If I unplug my toaster and poke it with a knife to retrieve a mangled piece of burnt toast, could I get a shock from any of the components?

• Household appliances that are essentially heating elements, such as toasters, electric kettles and waffle irons, store no electricity and should be harmless when unplugged. The same is true of large, motor-driven devices such as refrigerators, vacuum cleaners and washing machines. Some appliances, however, have internal power supplies that change the incoming household current to high-voltage direct current. These use capacitors, which can store dangerous charges for minutes or hours, even after the device is unplugged. Examples of these are old-style radios using valves or tubes. The capacitors ...

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